Almost two weeks ago, someone on GNOME's Discourse forum asked whether the missing Google Drive support in GNOME 50 was a bug or a deliberate decision.
GNOME developer Emmanuele Bassi replied, confirming that Drive was no longer supported.
He went on saying that libgdata, the library that coordinates communication between GNOME apps and Google's APIs, has gone without a maintainer for nearly four years. Furthermore, GVFS dropped its libgdata dependency about ten months ago, and GNOME Online Accounts now checks for that before offering the Files toggle under its Google provider settings at all.